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Subject[PATCH 4.9 271/271] net/x25: fix nonblocking connect
Date
From: Martin Schiller <ms@dev.tdt.de>

commit e21dba7a4df4d93da237da65a096084b4f2e87b4 upstream.

This patch fixes 2 issues in x25_connect():

1. It makes absolutely no sense to reset the neighbour and the
connection state after a (successful) nonblocking call of x25_connect.
This prevents any connection from being established, since the response
(call accept) cannot be processed.

2. Any further calls to x25_connect() while a call is pending should
simply return, instead of creating new Call Request (on different
logical channels).

This patch should also fix the "KASAN: null-ptr-deref Write in
x25_connect" and "BUG: unable to handle kernel NULL pointer dereference
in x25_connect" bugs reported by syzbot.

Signed-off-by: Martin Schiller <ms@dev.tdt.de>
Reported-by: syzbot+429c200ffc8772bfe070@syzkaller.appspotmail.com
Reported-by: syzbot+eec0c87f31a7c3b66f7b@syzkaller.appspotmail.com
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/x25/af_x25.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -764,6 +764,10 @@ static int x25_connect(struct socket *so
if (sk->sk_state == TCP_ESTABLISHED)
goto out;

+ rc = -EALREADY; /* Do nothing if call is already in progress */
+ if (sk->sk_state == TCP_SYN_SENT)
+ goto out;
+
sk->sk_state = TCP_CLOSE;
sock->state = SS_UNCONNECTED;

@@ -810,7 +814,7 @@ static int x25_connect(struct socket *so
/* Now the loop */
rc = -EINPROGRESS;
if (sk->sk_state != TCP_ESTABLISHED && (flags & O_NONBLOCK))
- goto out_put_neigh;
+ goto out;

rc = x25_wait_for_connection_establishment(sk);
if (rc)

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